The invention relates to the securing of a data input device of a computer system. Many data input devices may be associated with a computer system. The present invention focuses in particular on touch-sensitive surfaces such as, for example, those used in a portable microcomputer, well known by the name of “touchpad” for a touch-sensitive surface without a screen, or “touchscreen” for a touch-sensitive surface with a screen. These surfaces may or may not be fitted with a screen. A touch-sensitive surface is generally used to point at an object displayed on a screen of the computer system. To do this, a user moves a finger over the touch-sensitive surface. The movement of the finger is detected by the touch-sensitive surface and is reproduced on the surface of the screen. The object pointed at may be a virtual button displayed on the screen or a datum which the user wishes to input. The user may be required to select the object pointed at. This selection operation may be performed by pressing a real button disposed close to the touch-sensitive surface or by pressing directly on the touch-sensitive surface itself. A switch actuated by the button or by pressing the touch-sensitive surface generates electrical information enabling the selection.
The invention is particularly useful in aeronautics for a touch-sensitive surface belonging to a system installed on-board an aircraft. The system includes one or more screens disposed on the instrument panel of an aircraft, a computer and one or more data input devices, including, for example, a touch-sensitive surface. The touch-sensitive surface may be used to select flight parameters displayed on the screen of the system or more generally to point at and select objects displayed on the screen of the system.
The aircraft may be subjected to turbulence which risks interfering with the pointing at and selection of the objects. More precisely, turbulence generates vibrations which may cause uncontrolled movements of the selection means. Even in the absence of established turbulence, slight acceleration phenomena to which the system is subjected may interfere with the selection of objects pointed at by the touch-sensitive surface.
The presence of an object such as, for example, a drop of water, an insect, a pen, a shirt or jacket sleeve of an operator on the touch-sensitive surface in vibratory environments may be enough to trigger the selection switch.
Attempts have been made to secure the data input device by avoiding the inadvertent triggering of the selection switch by adding a switch lock in series with said switch. The unlocking of the switch is subject to certain conditions such as the fact that the selection is compatible with an area of the touch-sensitive surface valid for a selection, or that the vibratory level is sufficiently low to enable the correct activation of the touch-sensitive surface and the switch.
This locking solution has a number of disadvantages, such as the definition of predefined areas limiting the use of the complete touch-sensitive surface, or such as blocked usage periods in vibratory environments, shocks or significant constant accelerations.
More generally, the locking device is disposed in series with the switch (upstream or downstream) and acts on the electrical information originating from the switch.